Flow control (data): Difference between revisions

Revision as of 21:57, 10 November 2018

Revision as of 20:02, 16 February 2019

Line 9:

{{Main | Stop-and-wait ARQ}}

Stop-and-wait flow control is the simplest form of flow control. In this method the message is broken into multiple frames, and the receiver indicates its readiness to receive data for eacha frame, theof message is broken into multiple framesdata. The sender waits for ana ACKreceipt (acknowledgement (ACK) after every frame for a specified time (called a time out). ItThe isreceiver sentsends tothe ensureACK thatto let the receiversender hasknow receivedthat the frame of data was received correctly. ItThe sender will then send the next frame only after the ACK has been received.

=== Operations ===

# '''Sender:''' Transmits a single frame at a time.

#Sender waits to receive ACK within time out.

# '''Receiver:''' Transmits acknowledgement (ACK) as it receives a frame.

# SenderGo receiveto step 1 when ACK withinis received, or time out is hit.

# Go to step 1.

If a frame or ACK is lost during transmission then itthe hasframe to beis re-transmitted again by sender. This re-transmission process is known as ARQ (automatic repeat request).

The problem with Stop-and wait is that only one frame can be transmitted at a time, and that often leads to inefficient transmission, because until the sender receives the ACK it cannot transmit any new packet. During this time both the sender and the channel are unutilised.